Ten-year survival data of patients with high-risk cervical cancer emphasize the need for extended-field irradiation, according to the Radiation Therapy Oncology Group. The absolute survival was 55% for the patients who received the extended-field irradiation vs 44% for patients treated with pelvic irradiation alone, data from RTOG protocol 79-20 show.
Patients with stage IB or IIA primary cervical cancers measuring 4 cm or greater in diameter and patients with stage IIB cancers were randomized to receive either standard pelvic irradiation or pelvic plus para-aortic irradiation. There were 337 analyzable patients in the study. "We believe the reason for the improved survival was patients who completely responded to the extended-field treatment had a lower incidence to distant metastases than their counterparts treated on the other arm of the study," says Marvin Rotman, MD, chair of the study. In addition, there was a significantly better salvage rate in the complete responders who later failed locally, he says.
Patients on the pelvic irradiation alone arm of the study received 40 to 50 Gy to the pelvic area in 4.5 to 6.5 weeks, 5 days a week. Patients treated with para-aortic irradiation received 44 to 45 Gy delivered in 4.5 to 5.5 weeks, 5days a week. The pelvis then received 20 Gy and the para-aortic fields were treated with an additional 15 Gy.
All patients also underwent brachytherapy to a total dose of 4,000 to 5, 000 mg/h of radium equivalents.
Disease-free survival was similar in both arms (40% for the pelvic irradiation alone arm and 42% for the pelvic plus para-aortic irradiation arm). Locoregional failure rates also were similar (35% for pelvic and 31% for pelvic plus para-aortic irradiation).
The cumulative incidence of grade 4 and 5 toxicities at 10 years in the extended-field arm was 8.4%, as compared with 3.8% in the pelvic irradiation only arm. Complications were found more often in patients with prior abdominal surgery, Dr. Rotman says.